Fix failure to load on julia 0.3 when cairo is not installed. Fixes #160.
Fix failure to load on julia 0.3 when cairo is not installed. Fixes #160.

Hydrotoast/Compose.jl,JuliaPackageMirrors/Compose.jl,jiahao/Compose.jl,dcjones/Compose.jl,yuyichao/Compose.jl